The "Grow" product itself isn't very good. All they do is buy some ETFs, then charge you 0.25% management fee every quarter. You can get the exact same results that they have, by buying the exact same ETFs that they bought, without paying their 0.25% management fee. Though i suppose there may be some barriers to but so many different ETFs for smaller investment sums.
The bonus 0.88% that they offer, offsets this management fee that you pay, to some degree. However, your funds are locked in for two quarters, in order to be eligible to earn the 0.88%. So you would have to pay them back 0.5%. Your net gain is 0.38%, in return for losing the flexibility to withdraw anytime you want.